Francesco sez, "Italian Company uses an RC scale model Submarine to lay fiber through city's sewage system. The submarine used is the NETPUNE SB-1 produced by Taiwanese company Thunder Tiger. It costs ca $600 and can be found in many US hobby shops. The NEPTUNE SB1 adopts a static diving system driven by a ballast tank with pump & motor unit. Start the pump to induct the water into the ballast tank. Control the amount of water in the ballast tank, the submarine can dive from the surface and stay underwater in static. Using the propulsion power unit and full elevator and rudder control, you can drive the submarine graceful sailing underwater."